The present invention relates to video cameras. More specifically, the present invention relates to a method and apparatus for improving image signals generated by a video camera by controlling the gain applied to the image signals.
Most modern video cameras utilize a charged coupled device (CCD) image sensor. The CCD image sensor typically includes roughly between 320,000 to 500,000 microscopically small light sensitive cells. An image for recording is projected via a lens on the video camera onto the CCD image sensor. The image projected onto the CCD image sensor charges the cells electrically. The brighter the incoming light, the more powerfully the cells are charged. The charged cells produce a charge image that includes a plurality of image signals that corresponds to light and color information of the recorded image.
Most video cameras require the exposure level of the CCD image sensor to be within a defined range for the CCD image sensor to produce image signals at a strength that forms a high quality charge image. When the exposure level is outside of the defined range, the recorded image may appear to be too dark or too bright. Proper exposure depends both on the amount of light entering the lens and the amount of time during which the incoming light forms a single video field. The amount of light entering the lens of the video camera may be regulated automatically or manually by adjusting the aperture of the iris. The amount of time allowed for storing the light in the CCD image sensor may be regulated by adjusting a xe2x80x9cmetaphoricxe2x80x9d shutter speed that governs the amount of time allowed for storing light in the CCD image sensor.
If the exposure level of the CCD image sensor cannot be adjusted to fall within the defined range, some cameras allow the strength of the image signals generated by the CCD image sensor to be amplified to improve the quality of the charge image. Videotographers using current video cameras who wish to amplify or apply xe2x80x9cgainxe2x80x9d to image signals are provided with only a limited selection of how the image signals may be amplified.